1. Field of the Invention
This invention general relates to multicarrier communication systems. In particular, this invention relates to systems and methods that allow a transmitter to enter and exit a Q-Mode.
2. Description of Related Art
Q-mode is being examined by ADSL standards bodies in the ITU-T in the development of the G.dmt.bis and G.lite.bis ADSL standards, both of which are incorporated herein by reference in their entirety. Q-mode is a low power transmission mode intended to save power by transmitting signals with lower PAR (Peak to Average power Ratio) with respect to normal steady state, i.e., full power, signals. The Q-mode signal with low PAR will often have the same average power as the normal steady state signals but since the peak power is reduced, power consumption can be reduced in the analog transmission circuitry. This is very important especially for saving power in telephone company central offices and remote cabinets where ADSL modems are often installed.
Current Q-mode proposals utilize a Q-mode xe2x80x9cfillerxe2x80x9d symbol with low PAR properties in order to save power at the transmitter. Discussion of this type of approach can be found in various ITU Documents, such as, BA-044, BA-045, HC-029R1, CF-033 and CF-040, all of which are incorporated herein by reference in their entirety. Other ITU proposals state that the filler symbol should be defined by the transmitter and communicated to the receiver during initialization, see BI-080 and D.87, both of which are also incorporated herein by reference in their entirety.
However, current systems suffer from a number of drawbacks. These exemplary drawbacks include the necessity of receivers being required to implement circuitry to detect Q-mode symbols on every DMT symbol. Furthermore, the entry and exit modes associated with the Q-mode lack robustness since the receiver needs to be able to distinguish a Q-mode symbol from a real information-carrying symbol.
In contrast, the exemplary systems and methods of this invention focus on a receiver transparent Q-mode, i.e., a Q-mode that is only implemented by the transmitter, wherein the receiver is unaware of the Q-mode state of the transmitter. In this type of Q-mode configuration, the transmitter could enter and exit Q-mode as desired while the receiver, could, for example, continue to function as if operating normally, such as in xe2x80x9cshowtime.xe2x80x9d Through this approach, it is not necessary for the receiver to detect the entry and exit of Q-mode by the transmitter.
Accordingly, exemplary aspects of the present invention relate to multicarrier communications systems. In particular, an exemplary aspect of the invention relates to conserving power at a transmitter.
Additionally, aspect of the present invention relate to allowing a transmitter to enter into a Q-mode while the receiver is unaware of the operational state of the transmitter.
Aspects of the present invention also relate to eliminating the need for a receiver to have Q-mode entry and exit detection capabilities.
Aspects of the present invention also relate to seamless changing into and out of a Q-mode between a transmitter and a receiver.
Additional aspects of the present invention relate to sending a plurality of symbols from a transmitter to a receiver wherein the receiver does not need to determine which of the symbols is a Q-mode symbol.
These and other features and advantages of this invention are described in, or are apparent from, the following detailed description of the embodiments.